WebSocket Close Codes: Understanding the Different Types and Their Meanings

WebSocket is a protocol that enables real-time communication between a client and a server. It has become increasingly popular in recent years due to its ability to provide fast and efficient data transfer. However, like any other technology, WebSocket is not perfect, and there are times when it may experience issues or errors. One such issue that WebSocket users frequently encounter is the WebSocket close code.

What is a WebSocket Close Code?

A WebSocket close code is a code that is sent from one endpoint to another in order to signify the end of a WebSocket connection. This code is used when either the client or server decides to close the connection, either intentionally or due to an error. There are many different reasons why a WebSocket connection may be closed, and each reason is assigned a unique close code.

Understanding the Different Types of WebSocket Close Codes

WebSocket close codes are categorized into three groups: normal closure, abnormal closure, and reserved closure. Let’s take a closer look at each group and the codes that belong to them.

Normal Closure

Normal closure codes are used when a WebSocket connection is closed intentionally and in a normal manner. These codes are reserved for situations where the connection is closed due to a user action or a clean shutdown. The following are the normal closure codes:

1. 1000: Indicates that the connection has been closed successfully.
2. 1001: Indicates that the endpoint is going away.
3. 1002: Indicates that the endpoint is terminating due to a protocol error.
4. 1003: Indicates that the endpoint is terminating due to an unspecified reason.
5. 1004: Reserved. This code is not used in WebSocket connections.
6. 1005: Reserved. This code is not used in WebSocket connections.
7. 1006: Indicates that the connection was closed abnormally, without sending or receiving a close frame.
8. 1007: Indicates that the endpoint is terminating because it received data that was not consistent with the message type.
9. 1008: Indicates that the endpoint is terminating because it received a message that violates its policy.
10. 1009: Indicates that the endpoint is terminating because it received a message that is too big for it to process.
11. 1010: Indicates that the client is terminating the connection because it expected the server to negotiate one or more extensions, but the server didn’t.
12. 1011: Indicates that the server is terminating the connection because it encountered an unexpected condition that prevented it from fulfilling the request.
13. 1012-2999: Reserved for future use.

Abnormal Closure

Abnormal closure codes are used when a WebSocket connection is closed due to an error or an unexpected condition. These codes are reserved for situations where the connection is closed due to an error or an abnormal shutdown. The following are the abnormal closure codes:

1. 3000-3999: Reserved for use by libraries, frameworks, and applications.
2. 4000-4999: Reserved for private use.
3. 5000-9999: Reserved for global use.

Reserved Closure

Reserved closure codes are codes that are reserved for future use. These codes have not yet been defined, and their meanings are not yet known. The following are the reserved closure codes:

1. 1004: Reserved. This code is not used in WebSocket connections.
2. 1005: Reserved. This code is not used in WebSocket connections.
3. 1012-2999: Reserved for future use.

How to Handle WebSocket Close Codes

When a WebSocket connection is closed, the endpoint that initiates the close will send a close frame to the other endpoint, which will then respond with a close frame of its own. It is important to handle WebSocket close codes properly in order to ensure that the connection is closed cleanly and without errors.

When handling a WebSocket close code, the first thing to do is to check the code itself. If the code is a normal closure code, then it can be assumed that the connection was closed intentionally and in a normal manner. If the code is an abnormal closure code, then it can be assumed that the connection was closed due to an error or an unexpected condition. If the code is a reserved closure code, then it should be treated as an unknown error.

Once the code has been identified, the next step is to take appropriate action based on the reason for the close. If the connection was closed due to an error, then the error should be logged and appropriate measures should be taken to prevent the error from occurring again in the future. If the connection was closed intentionally, then any necessary cleanup should be performed.

FAQs

What is a WebSocket?

A WebSocket is a protocol that enables real-time communication between a client and a server. It is used to provide fast and efficient data transfer, and is becoming increasingly popular in web development.

Why do WebSocket connections close?

WebSocket connections can close for a variety of reasons, including user actions, server shutdowns, network errors, and protocol errors. When a connection is closed, a close code is sent to signify the reason for the close.

How do I handle a WebSocket close code?

To handle a WebSocket close code, first identify the code and determine whether it is a normal closure code, an abnormal closure code, or a reserved closure code. Then take appropriate action based on the reason for the close.

What should I do if I encounter a WebSocket error?

If you encounter a WebSocket error, log the error and take appropriate measures to prevent the error from occurring again in the future.

Can I use WebSocket close codes in my own applications?

Yes, you can use WebSocket close codes in your own applications. However, it is important to use them correctly and to handle them properly in order to ensure that your application is reliable and error-free.